As per the upstream advisory:

OpenSSL TLS clients enabling anonymous ECDH ciphersuites are subject to a denial of service attack.

OpenSSL 1.0.0 users should upgrade to 1.0.0m. OpenSSL 1.0.1 users should upgrade to 1.0.1h.

Acknowledgements:

Red Hat would like to thank the OpenSSL project for reporting this issue. Upstream acknowledges Felix Gröbert and Ivan Fratrić of Google as the original reporters of this issue.

As per the upstream advisory:

By sending an invalid DTLS handshake to an OpenSSL DTLS client, the code can be made to recurse, eventually crashing in a DoS attack.

Only applications using OpenSSL as a DTLS client are affected.

OpenSSL 0.9.8 DTLS users should upgrade to 0.9.8za OpenSSL 1.0.0 DTLS users should upgrade to 1.0.0m. OpenSSL 1.0.1 DTLS users should upgrade to 1.0.1h. .

Acknowledgements:

Red Hat would like to thank the OpenSSL project for reporting this issue. Upstream acknowledges Imre Rad of Search-Lab as the original reporter of this issue.